The venous system includes a multitude of one-way bicuspid valves that permit substantially unidirectional blood flow toward the heart. These valves are particularly important in the lower extremities to prevent the pooling of blood. When the leaflets of the bicuspid valves fail to close properly, the valve is considered “incompetent” as it permits leakage of retrograde flow resulting in the abatement of flow towards the heart.
This potentially serious condition is known as “chronic venous insufficiency.” Symptoms can progress from unsightly “spider” or varicose veins to skin discoloration and painful skin ulcerations. The etiology of venous insufficiency is multifactorial, including a past history of thrombotic events, chronic venous stasis, and venous hypertension. Current treatments for venous insufficiency include elevation of the feet and compression stockings. While these can relieve symptoms, the underlying disease remains untreated. Surgical techniques are also employed in which native valves can be bypassed or replaced with autologous sections of veins having functioning valves.
Recently, various implantable medical devices and minimally invasive techniques for implantation of these devices have been developed to treat and repair undesirable conditions within body vessels. For example, implantable medical devices can function as a replacement venous valve, or restore native venous valve function by bringing incompetent valve leaflets into closer proximity. These devices are advantageously inserted intravascularly, for example from an implantation catheter.
However, post-implantation thrombosis and platelet deposition on surfaces of endovascular prosthetic valves may occlude the conduit defined by the endovascular prosthesis or compromise the functionality of an implanted valve by limiting the motion or responsiveness of moveable portions of the device such as valve leaflets. For example, stagnation of blood around implanted prosthetic valves may cause stiffening and thickening of valve leaflets, reducing the leaflets' functionality and possibly eventually occluding the body lumen.